As I got into a taxi I considered how very seldom it is that the ruling
passion ever dies. The Queen's Square mystery ought to shake Quarles's
resolution if anything could.

Zena was out when I got to Chelsea, but the professor seemed pleased
to see me.

"Are you out of work, Wigan?" he asked, looking at the clock.

I did not want him to think I had come with any deliberate intention, so
I answered casually:

"No. As a fact I am rather busy. I came out to Chelsea to think. Chelsea
air is rather good for thinking, you know."

"It used to be," he answered. "I'm glad I have given up criminal
hunting, Wigan."

"I still find excitement in it," I answered carelessly, "and really I
think criminals have grown cleverer since your time."

He looked at me sharply. I thought the remark would pique his curiosity.

"That means you have had some failures lately."

"On the contrary, I have been remarkably successful."

"Glad to hear it," he returned. "What makes you say criminals are more
clever then?"